python3--更加规范的读取配置文件

将python读取配置文件规范了， 以后可以直接拷贝这个函数，
不用再写了；

import yaml
import os, sys
import argparse
from lib.mytool import MySqlTools

class GetMyCfg:
  def __init__(self, file_name):
    os.chdir(sys.path[0])
    try:
      cfg_file = open(file_name, 'r', encoding='utf-8')
    except Exception:
      print('file %s not found!' % file_name)
      return
    else:
      self.cfg_data = yaml.load(cfg_file, Loader=yaml.FullLoader)
      cfg_file.close()
  def get(self, tag):
    return self.cfg_data.get(tag, None)

def read_cfg(default_cfg):
  parser = argparse.ArgumentParser()
  parser.add_argument('-f', '--file', help='config file', type=str, default=None)
  args = parser.parse_args()
  file_name = args.file
  if not file_name:
    file_name = default_cfg
  if os.path.isfile(file_name):
    return file_name
  else:
    return None

if __name__ == '__main__':
  default_cfg     = 'cfg.yml'
  config_file     = read_cfg(default_cfg)
  my_cfg          = GetMyCfg(config_file)
  mysql_cfg       = my_cfg.get('mysql')
  mysql_cfg['db'] = 'easyops'
  mysql_conn      = MySqlTools('mysql', **mysql_cfg)
  res             = mysql_conn.select('select * from app_info order by id desc limit 10;')
  print(res)
  print(type(res))
  mysql_conn.close()